Underfeed stoker for hot air furnaces



March 19, 1940. 1.. LEE

I UNDERFEED STOKER FOR HOT AIR FURNACES Filed July 30, 1955 5Sheets-Sheet 1 m w M M W? m 6/ L [W W I IM March 19, 1940. LEE 2,194,025

UNDERFEED STOIIER FOR HOT AIR FURNACES Filed July 30, 1936 5Sheets-Sheet 2 Y 0 Q 4Q; ATTORNEY firs H M i h 19, 1940. LEE 1 UNDERFEEDSTOKERDFOR HOT AIR FURNACES Filed July so, 1936 5 Sheets-Sheet 3ATTORNEY March 19, 1940. I L. LEE 2,194,025

UNDERFEED STOKER FOR HOT AIR FURNACES Filed July 50; 1936 5 Sheets-Sheet4 ATTORNEY Lew- L-E'E v March 19, 1940. LEE 2,194,025

UNDERFEED STOKER FOR HOT AIR FURNACES Filed July 30, 1936 5 Sheets-Sheet5 w IINVENTOR,

L'El 'F L'E'E K K BY 2 ATTORNEY Patented Mar. 19, 1940 NlTED STATESPATENT OFFICE illeii Lee, Youngstown, Ohio; Halfdan Lee, executor of theEstate of said Leif Lee, deceased Application .luly 3t), 1936, SerialNo. 93,513 i illaims. (en. rec-r) The present invention relates to anair heating furnace and more particularly to a furnace utilizingautomatic stoker means for burning coke or other solid fuel.

i The primary object of the invention is to provide an emcient airheating furnace which is inexpensive to construct, economical inoperation, and which may be operated with a minimum of attention.

More specifically an object of this invention is to provide an airheating turnace which relies principally on radiation for its heatingefiect and in which the counterfiow principle is used and appliedbetween the incoming cold air and the i outgoing heated air and betweenthe flow of flue gases and the flow of the air being heated.

Another object of the invention is to provide a novel stolzer mechanismwhich is simple in design and which is operative to under feed coke orother solid fuel to a heel of live coals, to agitate the bed and todispose of the ashes.

Another object of the invention is to provide a novel combination of afurnace, air ducts associated therewith and automatic stoker means to 5form a highly eficient self-contained heating unit operable with aminimum oi attention.

A further object of this invention is to provide novel means to regulatethe flow of secondary air above the grates automatically in response tothe a pressure of the primary air below the grates or manually in such amanner that the primary air supply must be at its maximum before anysecondary air is allowed to enter the combustion chamber.

5 These and other objects and advantages of the invention will becomeapparent from a consideration oi the drawings and the followingspecification.

In the drawings:

Figure l is a side elevation of the assembled furnace with parts brokenaway and other parts in section.

Figure 2 is a part cross-sectional view taken along the linen-A ofFigure 1, looking in the direction of the arrows.

Figure 3 is a cross-sectional view taken along the line BB oi Figure 1,looking in the direction of the arrows. 7 s

Figure 4 is a cross sectional view taken along a the line -C of Figure1, looking in the direction of the arrows.

the line D-D oi Figure l,,loohing in the direction oi the arrows. l p

g Figure 8 is a c-sectional view similar to 5 is a cross-sectional viewtairen along Figure 3 but showing a modified means for supplying air forcombustion. v

Figure 7 is a top view of the air controlling means of Figure 6.

The heater and stoker assembly is supported on d a floor plate Ill whichin the illustrated embodi-- extending along the lower portion of theiroutside walls for communication with the space within the combustionchamber. A wall 'l t of refractory material is supported by and extendsalong the top of each duct it. The refractory material is preferablylight in weight so that it will not store a large amount of heat.

Extending transversely of the ducts at the ends thereof are the twosupporting plates ii and it which constitute spaced supporting means forthe grate bars i9. The grate bars are preferably tour in number,although any number may be and as shown they are provided withaplurality of perforations for supplying air to the fuel placed on thegrates. The grate bars it are longitudinally oscillatable and are placedadjacent each W other for a purpose to be'later' described.

[inv outer casing supported on floor plate it encloses the entireassembly including the furnace, stoirer and hopper. An intermediatecasing 21 is housed within but spaced from the outer casing cs- 2t andis spaced from but followsthe general contour of the arch-shaped casingii of the combustion chamber. At its lower end the intermediate casing277 is flanged outwardly at 20 to engage against the inner surface ofthe side wall of the outer casing 2h. The spaces between the outercasing and the intermediate casing constitute ducts for the passage ofcold incoming air while the spaces between the arch-shaped casing ii andthe intermediate casing 21 constitute ducts for the passage oi air beingheated by the combustion of fuel within the casing l I.

Positioned forwardly of the combustion chamher and on either sidethereof is a circulating fan housed in the fan casing 25 having itsinlet faced toward the center of the assembly. A fuel hopper havingslanting side walls H is positioned above and between the two fancasings and a portion of the lower surface of the walls 2| constitutes aportion of the side walls of-the ducts connecting the 5 s 1 5 with coalor coke dust emitted by the operation of the stoker mechanism.

A cross duct 3| utilizing a portion of the lower surface of the slantingwall 2| of the hopper as a wall and a portion of the outer casing 20 asan- 1 other wall interconnects the inlet ducts of the two fans. Thepurpose of this duct is to equalize the pressure .existing in the inletducts of the fans. This results in an equal volume of air passingthrough each fan and over each side of the heatingsurface II andconsequently uniform and more eflicient heating of the air.

The fans 25 discharge into the space between the casing II and the outercasing at the bottom of the furnace below the flange 28. The,

20 air passes upwardly in intimate contact with the corrugated surfaceof casing ll within the intermediate casing 21 and out through theoutlet at the top of the furnace. The path of travel of the incoming andoutgoing air is indicated throughout the drawings by arrows which showthe application of the counterflow principle.

The products of combustion pass upwardly from the space between therefractory walls l6 and into the dome of the arch-shaped casing II fromwhere they are drawn downwardly in contact with the inner surface ofcorrugated sheet H be tween the sheet and the outer surface of wall I 6.Since the inlet openings'l5 of conduits l4 are near the bottom of thefurnace, the. flue gases are required to travel substantially to thebottom of casing ll before they escape from adjacent the surface of thecasing I I. It can thus be seen that the flue gases are directeddownwardly along the inner surface of casing ll whereas'the fan dis- 0.charged air is caused to flow upwardly along the outer surface of easingll.

Conduitsdl are connected at one end with a header 23, a box-like ductone wall of which is the lower portion of end wall I 2. The duct 23 43discharges into the longitudinally extending duct 24 which in turndischarges into the cross duct 26 which may be connected with a stack ateither.

end thereof.

As shown in Figures 1, 3 and 4, a small trans- 0 versely extending duct32 is positioned along the top of header 23 and under the grate bars IS.The duct is open at its ends and is in communication with the dischargeof the fans. The center portion of the rear wall of the duct is cut awayat 33 to allow air coming into the ends of the duct to flow beneath thegrate bars l9 to supply primary air for combustion.

Longitudinally-spaced from the end wall l2 of the combustion chamber isthe parallel plate 22 which forms the rear wall of the hopper and thefront, end of the space between the inner casing II and the intermediatecasing 21. Plates l2 and 22 are provided with aligned openings toaccommodate the grate bars I! and passage of 55 fuel from the hopperinto the combustion chamber. Plates 34 connect the side edges of theopenings for a portion of their length, a small opening 36 being left atthe top on either side thereof. A bent strip 35 is positioned betweenthe plates 70 I2 and 22 and seals the space between the plates l2 and,22 from communicatioi with the combustion chamber. The plates I2, 22 and34 and the strip 35 form conduits for the entry of secondaryair forcombustion. The inlets of these 1 conduits are in communication with thedischarge of the fans 25 and are controlled by pressure responsivevalves 31 which are normally held closed by springs 38 but which areadapted to open and admit air above the grate bars I! when the fan hasattained a predetermined discharge pressure, the extent of opening beinggoverned by the pressure attained.

A gate 39 having a rearwardly bent lower end 40 extending into thealigned opening in plates [2 and 22 is slidably supported on the frontsurface of plate 22 by straps 4| which may be adjustably anchored inlugs 42 by pins 43 passing through an eye in the upper end of straps 4|.The bent end 40 of gate 39 supports an L-shaped block 44 of refractorymaterial which extends the width of the aligned openings in plates l2and 22. As shown, one side of the block 44 engages the inner surface ofplate l2 and the block 44 is provided with an enlarged lower portion 45to engage and be supported by the portion 4| of gate The inclinedsurface of portion 45 of the refractory block 44 is provided with aplurality of spaced parallel grooves 46 therein which in conjunctionwith the plate 40 form a plurality of secondary air conducting orificesdirected towards the grate bars l9 and into the furnace. As shown, theorifices are in communication with the secondary air conduit formed bythe strip 35.

The grate bars I! are arranged to oscillate longitudinally out of phasewith each other and they may either be moved manually or be powerdriven. I have shown a preferred. arrangement whereby the grate bars arepower driven and in which the connecting rods 48 are utilized to connectthe ends of the bars with the cranks of the crankshaft 50. Theconnecting rods 48 are pivotally connected with the grate bars by thepins 49. Crankshaft 50 is slowly driven by a pawl and ratchet mechanism5253 operated by an arm 54 oscillated by the crank 56 through an arm 55.A variable speed electric motor 58 is adapted to drive crank 56 throughsuitable reduction gear ing 51. As shown, the cranks of the crankshaft50 are angularly spaced 90 from each other. The purpose of thisarrangement is to insure relativemovement between adjacent bars andmovement in opposite directions of adjacent bars at least during part ofone revolution-of the crankshaft and this results in agitating the bedof live coals on the grate bars and causes coals or lumps of solid fuellying on the grate bars to be angularly oscillated.

The ends of the grate bars l9 extend beneath the outlet of the hopperand are each provided with a transverse shoulder 60 which propel solidfuel from the hopper along the path of travel of the grate bars. Thefuel is prevented from returning in the direction of the hopper bypressure exerted by fuel sliding down the inclined wall 2| of thehopper. If desired, the inner surface of wall 2| may be lined withglazed tile or other smooth surfaced material to lessen friction betweenthe fuel and the plate 2| and to prevent abrasion of the metal plate 2|.

Extending across'the rear end of the furnace above and to'the rear ofthe grate bars is the member 6| which has a depending lip the roundedlower surface of which is positioned slightly above the upper surface ofthe grate bars and slightly to'the rear of the end of the bars when thebars are in retracted position. This allows a small space between theedge of the grate bar and the lip when'the grate bar is in retractedposition to provide a passage for ashes but which prevents thefalling-of unburnt pieces of coal or coke by arresting their furthermovement. The ashes are shoved oif the plate H by the ends of the gratebars and fall into the pan. 63 which pan may be removed through door 62.

It can thus be seen that the grate bars perform a plurality offunctions, i. e., support the fire bed admit air thereto, agitate-thebed, feed fuel tion.

thereto and dispose of the ashes. The operation is such that the fuel iscaused to be moved along the surface of the bars and thus under feed thefire. The lumps of fuel move into the fire zone with an erratic motiondue to the relative movement of adjacent grate bars. The motion may bedescribed as composed of linear, rotation and angular oscillationmovements. An important result achieved by this feature is that the firebed is agitated and a normally adequate supply of primary air forcombustion is insured. Another result is that clinkers do not form asthe relative erratic movement of the pieces of fuel effectively preventamalgamation orfusion of the pieces which is the chief cause of clinkerforma- The operation of the device is obvious. A door 64 is providedwhereby access may be had to the combustion chamber for the purpose ofstarting the fire. Fuel is fed from the hopper in the man- --nerheretofore described. The quantity of fuel consumed and consequently therate of heat delivery is determined by the vertical position of gate 39and the speed of motor 58 which drives the grate bars I 9 and the fans,the fans bein mounted on shaft 65 driven bymotor 58 through pulleys 66and 61 and belt 68. Within certain limits of operation the automaticdampers 31 controlling the supply of secondary air for combustion remainclosed but for higher rates of operation when the permeability of thegrate bars and bed of live coals is such that an insufficient supply ofprimary air can reach the points of combustion the dampers 31 open inresponse to an increase of pressure from the fans and allowsecondary airto flow to the bed of coals along the path previously described. Theresult is an intensification of the combustion with a consequentincrease in the heat output.

Figures 6 and 7 illustrate a modification of the invention whereinprimary and secondary air for combustion is taken directly from theatmosphere and natural draft is relied on-to supply such air. Theconduit 32 instead of being in communication with the discharge-of thefans is connected with the atmosphere by means of a conduit 14communicating with an opening II in the side wall of the outer casing20. Another opening 12 in the outer casing is provided directlyabove'the opening H and allows secondary 'air to pass from theatmosphere to the conduit formed by strip35 through a duct I3. Theopeningsflll'and I2 are controlled by a valve 15 which is cylindrical inshape to rotatably fit within the curved indentation of the sidewall atthe openings II and "I2.

The cylindrically shaped valve is rotatably sup- 15 so that the upperopening 12 cannot be opened when the lower opening H is closed. Thearrangement is such that the lower opening must be completely openbefore any portion of the upper opening may be uncovered. This meansthat the maximum supply'of primary air must be furnished before anysecondary air can be admitted.

If desired, the chain ILmay be coupled with means controlling the speedof operation of the motor 58 whereby when the'motor is controlled to runat a predetermined speed, either the opening II or both openings II and12 may be uncovered.

While I have shown but one valve 15 it is obvious that another may alsobe employed-positioned on the opposite side of the furnace.

Having thus described my invention what I claim is:

1. An air heating furnace comprising a casing constituting a fuelsupporting and combustion chamber, a pair of spaced ducts arrangedlongitudinally in the lower portion of said casing and spaced from theside walls of said casing, a refractory wall supported on each of saidducts, a grate structure between said walls, each of said ducts havingopenings in its outer side wall opposite the adjacent side wall of thecasing, means connecting said ducts with a flue, and means to supply airto the space beneath the grate structure. v

2. An air heating furnace comprising a casing, a plurality oflongitudinally mov ble grate bars extending longitudinally into'saicasing. a hopper positioned at one end of saidasing, the outer ends ofsaid bars positioned belo the outlet of said hopper andprovided withmeans to propel fuel from said hopper into said casing, a pair of ductsarranged longitudinally within the lower portion of said casing oneither side of said bars, a refractory wall supported on each of saidducts and spaced from the adjacent side wall of the casing, meanspositioned beneath said hopper to connect said duets with a fiue andmeans to supply air to the space beneath said bars.

3. An air heating furnace comprising a casing forming a combustionchamber, fuel supporting means in said casing, a fuel hopper. adjacentone end of said casing, said fuel supporting means being movable andoperative to move fuel from the hopper into the casing, a flue duct inthe lower beneathsaid hopper, an air circulating device on either sideof said duct arranged to circulate air in heat exchanging relation withthe outer surfaces of said casing, and means positioned beneath saidhopper and between said air circulating devices to operate the fuelsupporting and moving means.

